Won't work reliably through an external keyboard USB port, if that's what you mean. I work in a shop, and use several different USB drives, most are not self-powered, and use on almost any Mac. Some are PowerBook G4s, which, IMHO, are the poorest Macs for lacking power to the USB ports. I run into some that don't work, but most will bus-power the USB drives that I have. Your Experience May Prove to be Different.
Again, for the most reliable results - use a powered USB external hub. Or, a self-powered USB drive.
If you want a reliable USB to hard drive connection, then trade off the G4, and get one of the aluminum MacBooks, or MacBook Pro. I see MUCH improved file transfers through USB, and devices mount much more quickly than any previous Mac I have used. I read about some problems with the new NVIDIA chipset on those models, but USB performance is not one of those problems, in my experience.... (just a recommendation!)